The present invention relates to building interior construction techniques, and more specifically to the construction of ceiling support systems beneath floor joists.
While traditionally, floor joists were made of solid wooden planks measuring 2″×10″ or 2″×12″, more modern construction techniques have replaced the solid wooden planks with composite solid wooden “I” beams or even solid steel “C”-channel joists. In conventional practice, furring strips, typically made of steel, and also referred to as “hat channel” strips, are fastened to undersides of the joists using fasteners, preferably screws. The fasteners pass through flanges of the furring strips and engage the underside of the joist. Next, wallboard panels, whether gypsum-based or made of other materials, including but not limited to structural cement, or other more water-resistant materials, are secured to the furring strips, by fasteners such as nails or screws. In many cases, multiple layers of wallboard panels are secured to the furring strips to create a ceiling, as is well known in the art.
To comply with local building codes, structures need to meet certain fire test standards promulgated by Underwriters Laboratories (UL) or ASTM International (ASTM). The fire test procedures and criteria differ with the geographic location and the type of construction. In conducting fire tests of ceiling assemblies attached to joists, it has been found that when steel “C”-channel joists and steel furring strips are constructed, during a regulated fire test, the furring strips tend to react to thermal expansion by bending or deforming, which cause breaches in the ceiling panels attached to the furring strips. Since wallboard panels often have fire retardant properties, once the ceiling panels are breached, the ceiling system succumbs to fire more rapidly than when the ceiling panels remain intact. In some cases, due to this bending or deforming of the furring strips, such systems have failed the designated fire test.
Thus, there is a need for providing an improved ceiling system attached to joists, which addresses the above-identified drawback.